Desmosomes are highly dynamic cell-cell adhesion complexes that have the ability to adjust their adhesive properties and molecular composition, thereby affecting cell migration, cell sorting and cell differentiation. One mechanism by which this is achieved is a change in the ratio of desmosomal cadherins [desmocollins (Dsc) and desmogleins (Dsg)] that are assembled into the desmosome. Very little is known about the gene regulatory pathways that control desmosome function during skin and skin appendage development. The goal of the present application is to determine how the expression of the Dsc genes is regulated during skin appendage (e.g. hair follicles, mammary gland) development. We have already identified transcription factors from the Wnt, NFkB and Notch signaling pathways that differentially regulate Dsc genes in cultured cells. To test our hypothesis that these transcription factors also control Dsc gene expression in cultured keratinocytes and in developing skin appendages, we propose the following specific aims: 1.) To analyze the effects of major signal transduction pathways on the expression of desmocollins in vitro. 2.) To determine the effects of Wnt Signaling on Dsc2 and Dsc3 gene expression during development. 3.) To use an in vivo complementation assay to determine whether Wnt signaling is required for Dsc3 function in vivo. The results of this project will lead to a better understanding of how morphogenetic processes, such as appendage formation, are regulated during development. Furthermore, understanding the regulation of desmosomal genes will help to develop new concepts in the therapy of acquired and inherited diseases caused by impaired desmosome function. Project Narrative: The goal of this project is to identify gene regulatory pathways that control desmosome function during mammalian development, in particular pathways that control the formation of the skin and its appendages (e.g. hair follicles, mammary glands).